Introduction & Methodology

This analysis reports on the incidence of cancer within the Scottish Borders NHS health board. Data includes cancer incidence by cancer site and gender for the years 1994 - 2018 and can be found here.

Each cancer site is classified according to the ICD10 code, an alpha numeric code which corresponds to each type of cancer and where it is found in the body. The data set includes individual ICD codes as well as ICD code groupings. I have chosen to include the individual ICD codes where possible when identifying the most common cancer sites. For totals and aggregates, I have used the grouped ICD10 codes.

This analysis focuses on the total number of new cancer registrations, the crude rate per 100,000 person-years at risk as well as the standardised incidence ratio (SIR) of each cancer type. The EASR and WASR have not been included as this report focuses solely on admissions within the Borders health board, and is not to be used to compare cancer rates with other nations.

Findings

Summary Statistics from 2009-2018:

  • There are an average of 1082 cancer registrations per year.

  • The most common cancer admission (accross men and women) is Non-melanoma skin cancer, equaling 291 admissions per year, accounting for 27% of all registrations.

  • Of all cancer registrations, females accounted for 506 registrations per year, and males for 577 registrations.

Cancer registrations by cancer site and gender

  • Non - melanoma skin cancer account for the most registrations across both genders, and is higher in men
  • Breast and prostate cancer for females and males respectively were the next most occurring cancers
  • Colorectal, trachea, bronchus and lung cancers occurred at similar rates across both genders

Crude rate of cancer incidence over time

Among females:

  • There is quite a lot of variation in crude rates from year to year
  • Non-melanoma skin cancer appears to be increasing
  • There appears to be a slight increase in breast cancer incidence and trachea, bronchus and lung cancer

Among males:

  • Non-melanoma skin cancer appears to be on the rise
  • Prostate cancer is also showing signs of increase
  • Other cancer types seem to be fairly stable

Which cancers are showing higher/lower incidence than expected?

Standardised Incidence Ratio (SIR)

The standardised incidence ratio (SIR) is used to determine if the occurrence of a certain type of cancer is higher or lower than expected, given the population and age distribution of the community.

If the SIR is greater than 100, it indicates that the cancer rate is higher than expected in that particular population. If the SIR is lower than 100, the cancer rate is lower than expected,

Care must be taken to interpret the SIR, as often the confidence limits can have a very large range. If the lower 95% CI is less than 100, and the upper is more than 100, it is possible that the true SIR does not deviate from 100 (is as expected). Furthermore there must be sufficient cases of cancer registered, and a sufficiently narrow confidence interval range for robust interpretation.

The criteria for selecting cancer sites with unexpected incidence are as follows:

  • incidence greater than 5
  • confidence intervals that do not overlap 100
  • confidence interval range of less than 500

  • Kidney (in males) and breast cancer (in females) were the only cancers to show lower than expected cancer incidence
  • Skin cancers appear to be occurring in rates higher than expected in males
  • Females are showing a higher than expected incidence of multiple myeloma

Conclusion